Scanning optical system

ABSTRACT

A synthetic resin lens for an optical system of a scanning optical system comprises a synthetic resin lens having a guide hole for an adhesive curing promoting light formed at a mount area thereof.

This application is a division of application Ser. No. 07/813,495, filedDec. 26, 1991, now U.S. Pat. No. 5,377,038.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a scanning optical system which is usedin an information recording apparatus such as a laser beam printer.

2. Related Background Art

FIG. 1 shows a plan view of a scanning optical system of an informationrecording apparatus and FIG. 2 shows a sectional view thereof. A laseroscillator 2, a collimator lens 3 and a cylindrical lens 4 are securedto a side wall of an optical box 1 and a polygon mirror 5 is mountedtherein. A spherical lens 6, a toric lens 7 and a reflection mirror 8are sequentially arranged in a direction of outgoing light beam.

The laser beam emitted by the laser oscillator 2 passes through thecollimator lens 3 and the cylindrical lens 4, is deflected by thepolygon mirror 5, and it is fθ-corrected by the spherical lens 6 and thetoric lens 7, and a resulting scanning light beam is reflected by thereflection mirror 8 and directed to a photoconductor drum which is aninformation recording medium.

In the prior art scanning optical system, the spherical lens 6 and thetoric lens 7 are made of glass and the glass lenses are secured to theoptical box 1 by ultraviolet ray cured adhesive so that the curing ofthe adhesive is promoted by irradiating an ultraviolet ray through thelens.

Recently, lens made of synthetic resin are frequently used in order toimprove the productivity of the lenses, reduce the weight, reduce thecost and improve the performance by non-spherical planes. A preferablematerial of the synthetic resin is polycarbonate resin in view of goodoptical characteristic, small change of dimension by humidity andphysical strength.

However, polycarbonate resin has a lower ultraviolet ray transmissionthan that of glass and it has only one fourth or fifth of the glasstransmission. When it is to be secured by the ultraviolet ray curedadhesive as it is in the prior art glass lens, the following problem isencountered. The ultraviolet ray irradiation time is long and theworkability is low. The adhesive is not uniformly cured due to ununiformirradiation. If the intensity of the ultraviolet ray is too high, thepolycarbonate resin is deteriorated by a photo-oxidization reaction.

SUMMARY OF THE INVENTION

It is an object of the present invention to eliminate the above-noteddisadvantage peculiar to the prior art and to provide a highly reliablescanning optical system which permits short time bonding of a syntheticresin lens.

In order to achieve the above object, the scanning optical system of thepresent invention which uses the synthetic resin lens in the opticalsystem has a hole to guide an adhesive curing promoting light ray formedin a mount of the synthetic resin lens.

In the scanning optical system of the present invention, a light ray forpromoting the curing is directed through the guide hole when the lens ismounted so that the curing of the lens securing adhesive is promoted.

Further, in order to achieve the above object, the synthetic resin lensof the present invention for the laser scan of the scanning opticalsystem is securely bonded to a fixed base of the scanning optical systemby the ultraviolet ray cured adhesive and has an integrally molded thinmount which projects beyond an effective area of the lens.

In the synthetic resin lens of the present invention for the laser scanof the scanning optical system, the ultraviolet ray cured adhesive isapplied to a rear surface or a front surface of the projecting mount,and the lens is positioned on the fixed base and the ultraviolet ray isirradiated normally to the thin planar portion. In this manner, the lensis securely bonded to the fixed base in a short time.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a plan view of a prior art scanning optical system,

FIG. 2 shows a sectional view of the prior art scanning optical system,

FIG. 3 shows a plan view of a first embodiment of a scanning opticalsystem of the present invention,

FIG. 4 shows an A--A sectional view of FIG. 3,

FIG. 5 shows a plan view of a second embodiment of the scanning opticalsystem of the present invention,

FIG. 6 shows a sectional view of a lens in a third embodiment of thescanning optical system of the present invention,

FIG. 7 shows a perspective view of a fourth embodiment of the scanningoptical system of the present invention,

FIG. 8 shows a perspective view of a scanning synthetic resin lens ofFIG. 7,

FIG. 9 shows a sectional view of the scanning synthetic resin lens ofFIG. 7,

FIGS. 10, 11 and 13 illustrate a method for securely bonding thescanning synthetic resin lens, and

FIGS. 12, 14 and 15 show perspective views of the scanning syntheticresin lenses of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiments of the present invention are now explained indetail with reference to the drawings. The like elements to that of theprior art are designated by the like numerals and the explanationthereof is omitted.

FIG. 3 shows a plan view of the scanning optical system of the presentinvention. A laser oscillator 2 is inwardly mounted on a side wall of anoptical box 11, and a collimator lens 3 and a cylindrical lens 4 aresequentially arranged on an optical axis of the laser oscillator 2, anda polygon mirror 5 is arranged on an extended line thereof. A sphericallens 6, a toric lens 17 and a reflection mirror 8 are sequentiallyarranged along a reflection path of the polygon mirror 5.

The toric lens 17 is made of polycarbonate resin, and it has cylindricallight guide holes 17a reaching from a top plane to a bottom plane formedbeyond an effective area at right and left ends. As shown in FIG. 4, aconcave lens plane 17b is formed at a bottom of the light guide hole 17aand it faces a mounting planar portion 17c which is a portion of thebottom of the toric lens 17.

To mount the toric lens 17 onto the optical box 11, a small amount ofultraviolet ray cured adhesive is dropped at a predetermined position onthe optical box 11, that is, a mount position of the toric lens 17, thetoric lens 17 is positioned so that the mounting planar portion 17c isput on the adhesive, and the ultraviolet ray is irradiated downwardthrough the light guide hole 17a. The ultraviolet ray is enlarged by theconcave lens plane 17b and irradiates the mounting planar portion 17c sothat the curing is promoted.

The cylindrical guide holes 17a which reach the bottom plane 17c fromthe top plane are formed in the vicinity of the left and right endsbeyond the effective area of the synthetic resin lens 17, and theultraviolet ray cured adhesive is applied between the inner bottom planeof the optical box 11 and the bottom plane 17c, and the ultraviolet rayis irradiated downward through the guide holes 17a to secure the lens17. While the ultraviolet ray goes through the synthetic resin from thebottom plane 17b of the guide hole 17a to the bottom plane 17c, it isnot substantially attenuated because of a short length and irradiatesthe adhesive to cure it.

FIG. 5 shows an inner side view of an optical box 21 of a secondembodiment of the present invention. A toric lens 27 made ofpolycarbonate resin has cylindrical light guide holes 27a extending froma rear surface to a front surface parallely to an optical axis formedbeyond an effective area of the toric lens 27 at right and left endsthereof. A bottom plane thereof is a concave lens plane 27b. Mountingplanar portions 27c are formed at right and left ends of the rearsurfaces of the light guide holes 27a, that is, the front surface of thetoric lens 27, and they are bonded to a rear surface of a fixed part 21awhich projects from the bottom of the optical box 21.

In the present embodiment, the toric lens 27 is abutted against themounting planar portion 27c through the ultraviolet ray cured adhesiveapplied to the fixed part 21a, and the ultraviolet ray is directedhorizontally through the light guide holes 27a.

FIG. 6 shows a sectional view in the vicinity of a toric lens in a thirdembodiment of the present invention. A light guide hole 37a isvertically formed in a toric lens 37 as it is in the first embodiment,but a bottom plane of the toric lens 37 is a convex lens plane 37b sothat an incident ultraviolet ray is focused to a mounting planar portion37c of the toric lens 37.

Since the ultraviolet ray is focused by the convex lens plane 37b, exactand efficient radiation of the ultraviolet ray is attained even if thebonding area to the optical box 31 is small. The efficient radiation ofthe ultraviolet ray is attained by the lens action of the bottom of thehole.

In any of the above embodiments, since the light path length of theultraviolet ray in the polycarbonate resin is shortened, the curing timeof the adhesive is shortened and uncured area due to ununiformirradiation is hard to appear.

While the toric lens has been explained in the above embodiments, thepresent invention is also applicable to other synthetic resin lenses.

In the scanning optical system of the present invention, the light pathlength in the synthetic resin is reduced by the depth of the guide holein the mount of the synthetic resin lens so that a stronger curingpromoting light ray is irradiated to the bonding surface. Accordingly,the lens securing time is shortened and the reliability is improved.

In a fourth embodiment of the scanning optical system for a laser beamprinter of the present invention, as shown in FIG. 7, a light beamemitted from a laser unit 41 which comprises a laser light source and acollimate lens passes through a cylindrical lens 42, is deflected by arotary polygon mirror 43 and is focused onto a photoconductor drum 46 bya scanning lens 45 including a toric lens secured to a fixed base 44.

A scanning synthetic resin lens to be explained later is used in thescanning optical system of the laser beam printer shown in FIG. 7.

FIG. 8 shows a perspective view and FIG. 9 shows a sectional view of thescanning synthetic lens of FIG. 7. Mounts 45a˜45d of tongue shapeproject at the opposite longitudinal ends of a thick scanning lens 45below the effective area of the scanning lens 45.

To securely bond the scanning lens 45 to a fixed base 44, adhesive isapplied to adhesive application areas 45a'˜45d' on the rear sides ofmounts 45a˜45d as shown in FIG. 10, the lens is positioned to the fixedbase 44 and the ultraviolet ray V is irradiated from the above to themounts 45a˜45d through an optical fiber F.

When the ultraviolet ray cured adhesive is used, a mercury tube having awavelength of approximately 357 nm, and a light power of approximately200 W˜1 KW is usually used as an ultraviolet light source. Thus, thetransmission of the ultraviolet ray is less than 1% for the prior artscanning lens 45 having the thickness of approximately 13 mm and theirradiation time of approximately 1˜2 minutes is required. In thescanning lens 45 of the present embodiment where the projection lengthof the mounts 45a˜45d is L1=5 mm and the thickness is L2=2 ˜3 mm, theultraviolet ray transmission is approximately 20˜30% and the securing ofthe adhesive is completed in several seconds. Thus, the irradiation timeof the ultraviolet ray is materially shortened and the unevenirradiation of the ultraviolet ray is eliminated. The thickness L2 ofthe projection of the scanning lens 45 is preferably 1˜5 mm. Themounting work is facilitated if the length L1 of the projection islonger than 1 mm, and preferably 3 mm or longer in order to improve theworkability in the securing operation.

The scanning lens 45 may be secured by forming a hole 44a in the fixedbase 44 and the adhesive is applied to adhesive application areas45a'˜45d' on the front surfaces of the mounts 45a˜45d to bond the lensto the fixed base 44, as shown in FIG. 11. In this case, the ultravioletray V is irradiated from the rear side of the scanning lens 45 throughthe optical fiber F, and the same effect as that of the bonding methoddescribed above is attained. The position of the optical fiber F has arelatively large degree of freedom and the height of the scanning lens45 may be reduced. Accordingly, this method is effective when anallowable height of the scanning lens 45 in the optical design is small.

FIG. 12 shows a perspective view of a scanning lens 47 in otherembodiment of the present invention. A thin mount 47a which extendshorizontally and then vertically is formed integrally with the scanninglens 47 at the bottom of the scanning lens 47. When the scanning lens 47is to be securely bonded to a fixed base 44, a step 44b which conformsto the contour of the mount 47a is formed on the fixed base 44 as shownin FIG. 13 and the lens is bonded by using the area of the mount 47afacing the step 44b as an adhesive application area 47a'.

The vertical positioning of the scanning lens 47 is attained without theadhesive by the formation of the mount 47b. It is effective when theallowable height of the scanning lens 47 in the optical design is small.The mount 47a may extend longitudinally of the scanning lens 47 asdescribed above, or may partially extend longitudinally so long as anecessary area to securely bond the lens is assured.

FIG. 14 shows a perspective view of a scanning lens 48 in otherembodiment of the present invention. Two thin mounts 48a and 48b areformed integrally with the scanning lens 48 beyond the effective area ofthe lens to project at the longitudinally opposite ends. A thin mount48c is also integrally formed in a side other than a bottom of thescanning lens 48 to project in a plane normal to the mounts 48a and 48b.

To securely bond the scanning lens 48 to the fixed base 44, a projection44c which abuts against the mount 48c is formed in the fixed base 44 andthe rear surfaces of the mounts 48a˜48c are used as the adhesiveapplication areas 48a'˜48c'. The positioning precision and thereliability to the bonding strength are improved by forming the mount48c on the side plane in addition to the bottom of the scanning lens 48.

The laser scanning synthetic resin lens of the present invention has theintegrally molded thin mounts which extend beyond the effective area ofthe lens. The ultraviolet ray cured adhesive is applied to the rearsurface or the front surface of the mount, and the lens is positioned tothe fixed base, and the ultraviolet ray is irradiated normally to thethin plane. In this manner, the bonding is completed in a short time,the number of steps is reduced and the cost is reduced. Since the mountprojects, the adhesive is evenly cured and the bonding distortion afterthe curing does not affect to the lens effective transmissive area.Thus, the deterioration of the optical characteristic is prevented.

FIG. 15 shows a perspective view of a scanning lens in other embodimentof the present invention. Unlike the above embodiments, a bonding plane52 of a synthetic resin lens 50 is a bottom surface of a thin projection51 which projects at a center bottom of the synthetic resin lens 50. Thesynthetic resin lens 50 is positioned in the manner described in theabove embodiment and the ultraviolet ray cured adhesive is applied tothe bottom surface of the thin projection 51. The projection 51 forbonding is integrally molded to project longitudinally of the lens inthe vicinity of the optical axis.

In the present embodiment, the synthetic resin lens 50 is secured to thefixed base 44 by the narrow area bonding by the bonding area 52, and nodistortion is created. An affect of the distortion to the effective lensarea is suppressed by increasing the distance between the thinprojection 51 and the effective lens area. Because the projection 51 isthin, the transmission of the ultraviolet ray is high and the bondingtime can be shortened.

In the present embodiment, the thickness of the projection 51 of thesynthetic resin lens 50 is preferably 1 mm ˜5 mm. The length of theprojection is longer than 1 mm to facilitate the mount operation, and itis preferably longer than 3 mm to improve the workability of thesecuring operation.

Since only one thin projection is used, the compact synthetic resin lensis attained.

What is claimed is:
 1. A synthetic resin lens for an optical system of ascanning optical system comprising:a synthetic resin lens; and a thinmount area projecting beyond an effective area of the lens, said mountarea being adapted to direct an adhesive curing light to adhesive insaid mount area and having a thickness of 1 to 5 mm.
 2. A syntheticresin lens according to claim 1 wherein the adhesive curing light is anultraviolet ray.
 3. A synthetic resin lens according to claim 1 whereina single mount area is formed in the lens.
 4. A synthetic resin lensaccording to claim 1 wherein a plurality of mount areas are formed inthe lens.
 5. A synthetic resin lens according to claim 1 wherein thelens is a toric lens.
 6. A synthetic resin lens according to claim 1wherein a length of the mount area is no smaller than 1 mm.
 7. Asynthetic resin lens according to claim 1, wherein the mount area isformed in a bottom and a side of the lens.
 8. A synthetic resin lensaccording to claim 1, wherein the mount area is formed at both sides ina longitudinal direction of the lens.
 9. A synthetic resin lensaccording to claim 1, wherein the mount area is formed at a part in thelongitudinal direction of the lens.
 10. A scanning optical systemcomprising:a light source; a deflector for deflecting a light beam fromsaid light source; a synthetic resin lens for directing the light beamdeflected by said deflector to a predetermined direction; a thin mountarea projecting beyond an effective area of the lens, said mount areabeing adapted to direct an adhesive curing light to adhesive in saidmount area and having a thickness of 1 to 5 mm; and a base for mountingsaid synthetic resin lens thereon.
 11. A scanning optical systemaccording to claim 10 wherein the adhesive curing light is anultraviolet ray.
 12. A scanning optical system according to claim 10wherein a single mount area is formed in the lens.
 13. A scanningoptical system according to claim 10 wherein a plurality of mount areasare formed in the lens.
 14. A scanning optical system according to claim10 wherein the lens is a toric lens.
 15. A scanning optical systemaccording to claim 10 wherein a length of the mount area is no smallerthan 1 mm.
 16. A scanning optical system according to claim 10, whereinthe mount area is formed in a bottom and a side of the lens.
 17. Ascanning optical system according to claim 10, wherein the mount area isformed at both sides in a longitudinal direction of the lens.
 18. Ascanning optical system according to claim 10, wherein the mount area isformed at a part in the longitudinal direction of the lens.
 19. Arecording apparatus comprising:a light source; a deflector fordeflecting a light beam from the light source; a recording medium; asynthetic resin lens for directing the light beam deflected by thedeflector to the recording medium, and a thin mount area projectingbeyond an effective area of the lens, the mount area being adapted to beirradiated by an adhesive curing light and having a thickness of 1 to 5mm; and a base for mounting the synthetic resin lens thereon.
 20. Arecording apparatus according to claim 19, wherein the adhesive curinglight is an ultraviolet ray.
 21. A recording apparatus according toclaim 19, wherein a single mount area is formed in the lens.
 22. Arecording apparatus according to claim 19, wherein a plurality of themount area are formed in the lens.
 23. A recording apparatus accordingto claim 19, wherein the lens is a toric lens.
 24. A recording apparatusaccording to claim 19, wherein a length of the mount area is no smallerthan 1 mm.
 25. A recording apparatus according to claim 19, wherein themount area is formed in a bottom and a side of the lens.
 26. A recordingapparatus according to claim 19, wherein the mount area is formed atboth sides in a longitudinal direction of the lens.
 27. A recordingapparatus according to claim 19, wherein the mount area is formed at apart in a longitudinal direction of the lens.
 28. A synthetic resin lensfor an optical system of a scanning optical system comprising:asynthetic resin lens; and a thin mount area projecting beyond aneffective area of the lens, said mount area being adapted to direct anadhesive curing light to adhesive in said mount area, and said mountarea projecting in a transverse direction of said lens.
 29. A syntheticresin lens according to claim 28, wherein the adhesive curing light isan ultraviolet ray.
 30. A synthetic resin lens according to claim 28,wherein a single mount area is formed in the lens.
 31. A synthetic resinlens according to claim 28, wherein a plurality of mount areas areformed in the lens.
 32. A synthetic resin lens according to claim 28,wherein the lens is a toric lens.
 33. A synthetic resin lens accordingto claim 28, wherein a thickness of the mount area is 1 mm to 5 mm,inclusive.
 34. A synthetic resin lens according to claim 28, wherein alength of the mount area is no smaller than 1 mm.
 35. A synthetic resinlens according to claim 28, wherein the mount area is formed in a bottomand a side of the lens.
 36. A synthetic resin lens according to claim28, wherein the mount area is formed at both sides in a longitudinaldirection of the lens.
 37. A synthetic resin lens according to claim 28,wherein the mount area is formed at a part in the longitudinal directionof the lens.
 38. A scanning optical system comprising:a light source; adeflector for deflecting a light beam from said light source; asynthetic resin lens for directing the light beam deflected by saiddeflector to a predetermined direction; a thin mount area projectingbeyond an effective area of the lens, said mount area being adapted todirect an adhesive curing light to adhesive in said mount area, saidmount area projecting in a transverse direction of said lens; and a basefor mounting said synthetic resin lens thereon.
 39. A scanning opticalsystem according to claim 38, wherein the adhesive curing light is anultraviolet ray.
 40. A scanning optical system according to claim 38,wherein a single mount area is formed in the lens.
 41. A scanningoptical system according to claim 38, wherein a plurality of mount areasare formed in the lens.
 42. A scanning optical system according to claim38, the lens is a toric lens.
 43. A scanning optical system according toclaim 38, wherein a thickness of the mount area is 1 mm to 5 mm,inclusive.
 44. A scanning optical system according to claim 38, whereina length of the mount area is no smaller than 1 mm.
 45. A scanningoptical system according to claim 38, wherein the mount area is formedin a bottom and a side of the lens.
 46. A scanning optical systemaccording to claim 38, wherein the mount area is formed at both sides ina longitudinal direction of the lens.
 47. A scanning optical systemaccording to claim 38, wherein the mount area is formed at a part in thelongitudinal direction of the lens.
 48. A recording apparatuscomprising:a light source; a deflector for deflecting a light beam fromthe light source; a recording medium; a synthetic resin lens fordirecting the light beam deflected by the deflector to the recordingmedium, and a thin mount area projecting beyond an effective area of thelens, the mount area being adapted to be irradiated by an adhesivecuring light, said mount area projecting in a transverse direction ofsaid lens; and a base for mounting the synthetic resin lens thereon. 49.A recording apparatus according to claim 48, wherein the adhesive curinglight is an ultraviolet ray.
 50. A recording apparatus according toclaim 48, wherein a single mount area is formed in the lens.
 51. Arecording apparatus according to claim 48, wherein a plurality of mountareas are formed in the lens.
 52. A recording apparatus according toclaim 48, wherein the lens is a toric lens.
 53. A recording apparatusaccording to claim 48, wherein a thickness of the mount area is 1 to 5mm.
 54. A recording apparatus according to claim 48, wherein a length ofthe mount area is no smaller than 1 mm.
 55. A recording apparatusaccording to claim 48, wherein the mount area is formed in a bottom anda side of the lens.
 56. A recording apparatus according to claim 48,wherein the mount area is formed at both sides in a longitudinaldirection of the lens.
 57. A recording apparatus according to claim 48,wherein the mount area is formed at a part in a longitudinal directionof the lens.